1. Field of the Invention
This invention relates to novel metal deactivators. More specifically, it relates to reaction or condensation products of aliphatic polyamines, beta-diketones and salicylaldehyde or substituted salicylaldehydes, the method of preparing these condensation products, and their use as metal deactivators in hydrocarbon fuels.
2. Description of the Prior Art
In the storage of gasoline, middle distillates, and other liquid hydrocarbon fuels, one of the greatest problems is the formation of gums, tars and undesirable colored impurities brought about by the degradation of these fuels when they are permitted contact with atmospheric oxygen. Oxidative degradation is catalyzed strongly by solubilized copper but also to a significant extent by solublized iron, cobalt, nickel, chromium and manganese present in the fuels. These metals are introduced into the fuels in the course of refining, storing and shipping.
One solution to this problem of oxidative degradation has been to add to fuels compounds which deactivate the solubilized metals, particularly copper, thereby suppressing their catalytic capacity and substantially reducing oxidative degradation.
Compounds which have been particularly utilized as metal deactivators are the condensation products of amines, particularly polyamines with aldehydes and ketones. U.S. Pat. Nos. 2,055,810; 2,181,121; 2,255,597; 2,264,894; 2,282,513; 2,301,861; 2,426,206; 2,461,894; and 2,533,205, disclose compounds of this nature for suppressing the activity of solubilized metals, particularly copper, in the oxidative degradation of hydrocarbon fuels.
Of the foregoing, the compounds disclosed in U.S. Pat. No. 2,181,121 have been the ones most widely used in industry. These compounds are obtained by condensing one mole of a polyamine containing at least two primary amine groups with at least two moles of an ortho-hydroxy substituted aldehyde which is aromatic in nature. Commercially, the compound most widely used has been the reaction product of salicylaldehyde and 1,2-propanediamine which has the following structure: ##STR1## and is known ordinarily as N,N'-disalicylidene-1,2-propanediamine or as 1,2-disalicylidenepropanediamine.
However, as pointed out in U.S. Pat. No. 2,462,688, N,N'-disalicylidene-1,2-propanediamine, while effective to deactivate copper, can be ineffective to deactivate chromium or nickel, and can actually promote the oxidant effects of manganese, iron and cobalt. A metal deactivator which will function to deactivate a greater range of metal contamination in hydrocarbon fuels is thus highly desirable.
As noted previously, one of the reactants utilized to make N,N'-disalicylidene-1,2-propanediamine is 1,2-propanediamine. The supply of 1,2-propanediamine appears currently to be diminishing so that it becomes necessary to turn to other more inexpensive and available polyamines. An obvious choice would appear to be the condensation product of the more plentiful ethylenediamine and salicylaldehyde, N,N'-disalicylidene-1,2-ethanediamine having the following structure: ##STR2## N,N'-disalicylidene-1,2-ethanediamine
Unfortunately, the condensation product of ethylenediamine with salicylaldehyde, in comparison to N,N'-disalicylidene-1,2-propanediamine is markedly less soluble in hydrocarbons, both itself and when it is complexed with copper and is functioning as a deactivator. This is demonstrated in the following data from page 84 of Technical notes 1963-64, Petroleum Chemicals Division, E. I. DuPont de Nemours & Co. (Inc.). The ethylenediamine salicylaldehyde condensation product is thus less effective as a copper deactivator. If one attempts to increase solubility by using homologous compounds of increased chain length, for example 1,6-diaminohexane, efficiency as a metal deactivator is substantially reduced.
______________________________________ Solubility of Deactivators and Their Chelates in Jet Fuels Salicylaldehyde Type of Copper Chelate Jet 1,2-Propane- Ethylene- 1,2-Propane- Ethylene- Fuel diamine diamine diamine diamine ______________________________________ Solubility at 32.degree. F, lb/1000 bbl A 370 142 1.0 0.04 B 930 107 -- -- C -- -- 0.5 0.1 D -- -- 6.5 0.04 E -- -- 0.6 &lt;0.04 F -- -- 1.0 0.04 ______________________________________
Accordingly, one object of this invention is to retard the oxidative degradation of hydrocarbon fuels and other liquid hydrocarbon mixtures. Another object of this invention is to provide a metal deactivating composition which will suppress not only the ability of solubilized copper to catalyze oxidative degradation in hydrocarbon fuels, but that of other trace metals such as manganese, iron, cobalt, nickel and chromium. Still another object of this invention is to make available a soluble metal-deactivating composition formulated, at least in part, from readily available and inexpensive ethylenediamine. Yet another object of this invention it to provide a method for making a metal deactivating composition having the foregoing desirable characteristics.